This invention relates to a cam-operated mechanism for clamping a vehicle steering column in a range of different adjusted positions.
A vehicle steering column can be adjusted in accordance with different user preferences. Typically, the adjustment can be a tilt type adjustment around a horizontal axis extending transversely across the steering column, about one foot in front of the steering wheel. The driver of the vehicle can operate a manual lever on the steering column near the steering wheel, to vary the plane of the steering wheel to an inclination he considers to be most comfortable or preferable from an operating standpoint. In some vehicles the steering column can be slidably adjusted, to move the steering wheel toward or away from the driver.
For safety reasons the steering wheel and steering column should be securely locked in any selected position of adjustment. In some cases the adjusting mechanism includes detent notches or ratchet teeth that provide a positive locking action. In other cases the adjusting mechanism includes a friction lock, usually plural friction disks that are moved together by a manually controlled mechanism. A friction lock is advantageous in that the steering column and steering wheel can have a relatively large or infinite number of adjusted positions, as opposed to a lesser number of discrete positions achieved with detent notches.
When the friction lock is operated by a cam mechanism the cam operator can include a rotary shaft extending through clearance openings in the friction disks. A cam on the shaft is aligned with a cam follower carried by one set of friction disks. Manual rotation of the shaft (by means of a manual lever carried by the shaft) causes the cam to exert an axial force on the cam follower, whereby the friction disks are brought into pressure contact with one another. The frictional pressure contact between the friction disks holds the steering column and steering wheel in any selected position of adjustment.
One problem with typical friction locks is that the frictional pressure force existing between the friction disks is transmitted through the cam follower onto the cam operator. The cam operator becomes frictionally locked to the cam follower, so that the person has some difficulty in moving the lever to the unlocked position. On the other hand, when the person attempts to move the manual lever from the unlocked position to the locked position, the build up of frictional forces can cause the cam operator to prematurely frictionally lock to the cam follower, so that the friction disks fail to lock together with a sufficient frictional pressure. When the person exerts pressure on the steering wheel the wheel can abruptly move from a stable position in an uncontrolled fashion.
The present invention relates to a friction lock mechanism for a steering column, wherein the interface between a cam operator and cam follower is comprised of anti-friction elements. When the driver swings the manual lever up or down, the individual anti- friction elements rotate to relieve frictional drag between the cam and cam follower. The manual lever can thereby be more easily moved to the locked, or unlocked, position. The friction disks can have a relatively high pressure contact without requiring an abnormally great manual force on the operating lever.
The rotary anti-friction elements can be carried by the cam follower or by the cam operator. In another arrangement the anti-friction elements can be floatably positioned between the cam and cam follower. Whatever the specific arrangement, the anti-friction elements minimize frictional drag between the cam and cam follower, with resultant advantages as regards a greater disk friction lock action and a lower manual operating force requirement.
Additional features and advantages of the invention will be apparent from the attached drawings and description of an illustrative embodiment of the invention.